1. Field of the Invention
The present invention relates to a method for separating blood into blood components aseptically in a closed system, which is useful for separately collecting leukocyte-removed blood components, particularly leukocyte-removed erythrocytes leukocyte-removed plasma, leukocyte-removed platelets, etc., from the whole blood of a healthy human. The present invention is also concerned with a blood components separator unit, which can advantageously be used in practice of the above-mentioned method.
2. Discussion of Related Art
In recent years, with the progress in medical science, particularly in immunology, there has been an increase in demand for transfusions of blood components. The blood component to be transfused is suitably chosen according to the purpose of therapy. In practicing the transfusions of blood components, leukocytes must be removed from the blood components for the following reason. The number of types of leukocytes is very large, differing from that of erythrocytes which, for example, is only 4 types, namely types A, B, O and AB under the ABO blood grouping system. Therefore, it is extremely difficult to match the blood type of leukocyte present in a blood component to be used for transfusion to the blood type of leukocyte of a patient who will be subjected to blood transfusion Therefore, when blood components from others are transfused into a patient without removing leukocytes therefrom, an antibody against the surface antigen present in the transfused leukocyte is produced in the body of the patient since such leukocytes contained therein, in most cases, are foreign substances to the body of a patient. The repeated transfusion of blood containing such foreign leukocytes causes the antigen-antibody reaction to occur between the produced anti-leukocyte antibody and the surface antigen of the transfused leukocytes, so that an adverse effect, such as fever and headache, is caused. In recent years, various filter means have been developed for removing leukocytes from blood components to be used for transfusions. Such filter means can remove leukocytes efficiently from whole blood or various blood components. Therefore, by the use of the filter means for removing leukocytes, the above-mentioned adverse effect can be suppressed.
Generally, in practicing the removal of leukocytes from whole blood or blood components by means of filter means, the filtering means is connected to a bag containing whole blood or blood components. However, it is difficult to connect the filter means aseptically to the bag unless a specific apparatus is used. Therefore, conventionally, in the removal of leukocytes, the leukocyte-removed blood or the leukocyte-removed blood components would be likely to be contaminated with various germs. Accordingly, it has been obligatory to use the leukocyte-removed blood or blood components within 24 hours after the preparation thereof. Therefore, it is earnestly desired in the art to develop an aseptic system for removing leukocytes from whole blood or blood components.
In U.S. Pat. No. 4,596,657, one aseptic system for removing leukocytes is disclosed. Illustratively stated, a multiple-blood bag system comprising a primary bag, at least two satellite bags connected to the primary bag through conduit means, and a filter means for removing leukocytes integrally disposed between the primary bag and one of the satellite bags is disclosed. The bag system is used in the following manner. Blood is collected in the primary bag and subjected to centrifugation so as to be separated into a plasma layer and an erythrocyte concentrate layer. The separated plasma layer is then transferred from the primary bag into a first satellite bag through conduit means which is fluid-tightly disposed between the primary bag and the first satellite bag. The erythrocyte concentrate layer is caused to pass through the filter means to remove by filtration leukocytes from the erythrocyte concentrate and the resultant leukocyte-removed erythrocyte concentrate is collected in the second satellite bag which is connected to the primary bag through the filter means. With this bag system, leukocytes present in the erythrocyte concentrate are removed, but leukocytes present in the separated plasma disadvantageously cannot be removed. Further, this bag system has the following disadvantages. That is, when the blood collected in the primary bag is separated by centrifugation, the filter means must be placed in a centrifuge together with the primary bag and the satellite bags, leading to a danger that the filter means and the bags are likely to be destroyed due to the centrifugal force and the friction between the bags and the filter means during the centrifugation Therefore, this bag system have not been widely used.
European Patent Application Publication No. 0 266 683 A2 discloses another bag system as a blood components collector unit This unit comprises a cannula, a blood collection bag, a filter means for removing leukocytes and a filter membrane type blood components separator which are connected through tubes. The unit also comprises a plasma collection reservoir and a blood cell collection reservoir, both of which are connected to the blood components separator through tubes, wherein each connection through each tube is in a fixed fashion, thereby providing a unified connection. By the use of this unit, whole blood collected from a donor can be separated into leukocyte-removed plasma and leukocyte-removed blood cell-enriched blood by filtration, using a combination of the filter means and the membrane type blood components separator. However, this unit has disadvantages in that the plasma collection ratio, i.e., the ratio of the amount of the filtration-separated plasma to the amount of the collected whole blood is small as compared to the plasma collection ratio obtained by centrifugal separation; that proteins having relatively high molecular weight which are present in plasma are likely to be prevented from passing through the filter membrane of the separator so that the recovery of such proteins in the separated plasma is low; that by the contact of whole blood with the membrane, complement components in the blood are unfavorably activated, causing the quality of the blood to be lowered; and that the membrane type blood components separator is expensive.